JPH01285407A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce pattern noise by forming one round of a tread by plural pitches with different lengths and specifying the pitch array in a fundamental period beginning with the shortest pitch, the kind of a pitch, the ratio of lengths of adjacent pitches, the number of fundamental periods, the pitch array rate to the whole peripheral length and the rate of the shortest period. CONSTITUTION:One round of a tread is formed by plural pitches with different lengths, in which the pitch period starts with the shortest pitch Pmin, and one period is formed including at least one longest pitch Pmax in one period. The pitch array in the fundamental period is set in such a manner that the secondary or more degree component in a step-formed waveform Fourier series expansion formed by inverse numbers of pitch lengths 1/Pa-1/Pd and pitch lengths Pa-Pd are 80-200% of the primary components. The ratio of length of the adjacent pitches is let be 1.02-1.45, the number of fundamental periods is let be 1-4, the pitch array/the whole periphery length is let be 60% or more, and the shortest fundamental period/the whole peripheral length is 1/7 or more. Thus, noise can be reduced.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a tire in which trend design elements having a plurality of different pitch lengths are arranged on the tread surface. This invention relates to a pneumatic tire that reduces pattern noise.

[Prior art]

Conventionally, in order to reduce pattern noise, efforts have been made to make the noise less noticeable by dispersing the pattern noise into a wide frequency band around the pitch frequency (a frequency determined by the number of tire rotations x the number of tread design elements). This is called the barrier pull pitch arrangement method, in which tread design elements with different pitch lengths (i.e., pitches) are arranged appropriately in the tire circumferential direction so that each tread design element makes contact with the ground contact surface. This is a method to prevent noise from concentrating on a specific frequency by changing the time interval of the pulsed noise or vibration that occurs when the noise is generated, and is based on frequency modulation theory used in radio engineering. However, pattern noise has not yet been sufficiently reduced.

Therefore, as a result of research aimed at reducing pattern noise, the present inventor found that the pulsation of the sound pressure level cannot be overlooked as a factor that worsens the feeling of tire noise.

In other words, even though the sound pressure levels averaged over a certain period of time as in conventional noise measurement methods are the same, the sound pressure levels may be superior or inferior in terms of the feeling in the human hearing room. Yes, when I investigated the cause of this, I found that
It has been found that there is a difference between a sound pressure level that pulsates significantly and a sound pressure level that does not pulsate in a low frequency band of about 10 Hz or less. To quantitatively observe the pulsation of this sound pressure level, which is one of the causes of noise,
This is possible by reproducing noise recorded at high speed at low speed and outputting temporal changes in sound pressure level. For example, a method similar to the JASOC606-73 tire noise test method is used, in which tires are transferred at 50 km/h on a steel drum with a diameter of 3000 am (air pressure, rim size, and load are JATM standard conditions), and the pulsation is evaluated as O.
It can be evaluated based on the variation range of the A value (overall value of noise that has passed through a bandpass filter of 100 to 2000 Hz) within one rotation of the tire.

On the other hand, in the conventional theory regarding the arrangement of tread design elements regarding sound pressure level, it is assumed that one sine wave is generated from one tread design element, and the time period in one tire rotation is the same as the arrangement order of the tread design elements. Generally, dispersion on the frequency axis is simulated by expanding a sine wave train that occurs at intervals into a Fourier series. In particular, a lot of theoretical analysis has been done regarding the regular sine wave arrangement of tread design elements with short circumferential length, that is, pitch length, from short tread design elements to long tread design elements, and then back to short tread design elements. Research and innovations are being carried out (for example, Automotive Technology Vol. 1.28, Patient 1, 197
4. Regarding Tire Noise”, JP-A-115-1987
(See Publication No. 801). However, in these considerations,
The reason why the aforementioned pulsation of the sound pressure level is not discussed is because the magnitude of vibration generated from each trend design element is assumed to be constant.

The present inventor focused on the fact that when the circumferential length of a tread design element is large, the vibration level generated from that element becomes large, and attempted theoretical calculations based on the following assumptions. That is, the vibration generated from each tread design element is expanded into a Fourier series on the assumption that it is a sine wave having a large amplitude in proportion to the circumferential length of the tread design element. As a result, Fig. 10 (a), (b) and Fig. 11 (a), (
As shown in (b), if it is assumed that sine waves of equal size exist from each trend design element using the conventional calculation method, no amplitude will appear in the low frequency band as shown in Figure 1 (b). However, if it is assumed that a sine wave with an amplitude commensurate with the pitch length of the tread design elements is generated, as shown in Fig. 11(b), in a low frequency band corresponding to the special number of cycles of the tread design element array. A peak of vibration can be seen. In particular, when the tread design elements are arranged in a regular manner, the peak in this low frequency band becomes noticeable, which increases the pulsation of the sound pressure level and worsens the feeling of noise.

FIG. 10(a) and FIG. 11(a) are explanatory diagrams showing the pitch arrangement (tread design element arrangement), respectively. 1 indicates a vibration waveform. FIG. 10(b) and FIG. 11(b) are relationship diagrams between orders and amplitudes corresponding to the orders when Fourier analysis is performed, respectively. In FIG. 10(a) and FIG. 11(a), the pitch length of pitch A = 31.7 mm, the pitch length of pitch B = 27.5 no+, and the pitch length of pitch C = 24
．． 5 m-, pitch group E, = CCCCCC, pitch group E
z ” B B B B B B B B, pitch group E3 = AA AA AA AA A, pitch group E
4=BBBB, pitch group E,=CCCCCC.

Pitch group Eb = BBB, pitch group E? =AAAAAA
A, pitch group E * = B B B B B B B
.

Pitch group E9 = CCCCCCCCCC, pitch group E,
@=BBBB, pitch group E, 1=AAAAAA, pitch group EIz=B B B B. The pitch arrangement in FIG. 10(a) and the pitch arrangement in FIG. 11(a) are the same. Here, "pitch" refers to the smallest unit of a tire tread design that is generally repeated in the circumferential direction. Furthermore, the term "pitch group" refers to a portion of the pitch where the same pinches are consecutively arranged.

[Purpose of the invention]

The present invention has devised a pitch arrangement in order to reduce the pulsation of low-frequency noise that occurs due to the regularity of the pitch arrangement, and improves the pulsation of the sound pressure level and reduces pattern noise. The objective is to provide pneumatic tires that improve the comfort and comfort of automobiles.

[Structure of the invention]

Therefore, in the present invention, one circumference of the tread surface is made up of a plurality of pitches having different lengths, and when the pitch length of the shortest pitch is P sin and the pitch length of the longest pitch is P□8, Pa17. At least one P, □ between the pitch at the beginning of the cycle and the pitch of P15 in the next cycle.
starting from a pitch of P sin to the beginning of the next period P, ! When the fundamental period is up to one pitch before the pitch of sometimes,
Components of second order or higher order are 80% to 200% of the first order component
(2) the number of types of pitches within the basic period is 3 to 8; (3) the ratio of the lengths of adjacent pitches of different pitch lengths within the basic period is 1.02 to 1. (4) the number of fundamental periods is 1 to 4;
(5) The pinch arrangement occupies 60% or more of the total circumference; (6) The shortest fundamental period is 1 of the total circumference.
The gist of this is a pneumatic tire that is characterized by occupying more than a Noah.

Hereinafter, the configuration of the present invention will be explained in detail.

The present inventor further attempted the following theoretical calculation regarding the pulsatility of the pattern noise described above. That is, we studied the composition of components in orders below the 10th when a step-like waveform formed by the reciprocal of the pitch length and the pitch length is expanded into a Fourier series. It can be easily inferred that in order to disperse the peaks that appear at low frequencies, it is sufficient to change the length of the period, similar to the conventional dispersion of pitch noise. In other words, as shown in Figure 1 (a) and (b), in an arrangement where the pitch length changes gradually from short to long and then back again in a sinusoidal manner, the pitch length changes from long to long. Since vibrations occur and small vibrations occur from short pitches, the change in the vibration level exactly matches the sine wave-like change in the pitch arrangement, and the number of repetition periods (Figure 1 (a)).

In (b), a large peak occurs at a low order corresponding to 3). Therefore, in the past, pitches with multiple types of pitch lengths were arranged to disperse pinch noise.
It is easy to see that it is sufficient to have multiple types of arrangement periods, as shown in Figures 2 (a), (b) and 3 (a).
(b) is calculated based on this idea by varying the length of each cycle.

Here, β indicates the ratio between the length of one cycle and the length of the next longest cycle. For example, the ratio between the length of the longest cycle and the length of the second longest cycle, It is the ratio between the length of the cycle and the length of the third longest cycle. In FIGS. 1(a) and 1(b), the period is equal to β-1. In Figures 2 (a) and (b), β = 1.4, the longest period is about 1/2 of the total, the second period is about 1/3, and the shortest period is about 1/4
occupies . Also, in Figures 3(a) and (b), β=2
．． 0, about 172, about 174, about 177 of the total, respectively.
occupies .

From these results, it is understood that when the length of each period is changed, the low-order peaks are slightly dispersed, similar to the conventional pitch noise dispersion. However, although the pitch noise dispersion is better as the number of periods is smaller, there is a drawback that if the number of periods is too small, the number of types of period lengths for measuring low-order dispersion is insufficient.

For example, if the number of cycles is 1, the cycle length cannot be changed.

Therefore, in order to maintain good dispersion of pitch noise, the present inventor reduced the basic number of cycles and incorporated complex cycles within one cycle to improve low-order dispersion. I calculated it. Figure 4 (a), (b)
Figures 5(a) and 5(b) show the addition of higher-order components than the fundamental period (consisting mostly of first-order components) to an array with three equal-length fundamental periods. Here, rl indicates the abundance ratio of the i-th component to the first-order component (fundamental period), and the first-order component is set to 1. In FIGS. 4(a) and (b), r! xi
, Q, that is, the second-order component is added to each fundamental period at the same rate as the first-order component. In Figures 5(a) and (b), r
2 = r3 = 1.0, that is, the second-order component and the third-order component are added to each fundamental period at the same rate as the first-order component. As can be seen from these figures, even when the fundamental period lengths are equal (β=1.0), when a higher order waveform is incorporated, the lower order dispersion increases dramatically. This is the first point mentioned above.
Figure (a).

This can be better understood by comparing the cases shown in (b) to (a) and (b) of FIG. Also, FIG. 6(a).

In (b), the fundamental period length itself is also varied by β-1, 2, and a second-order waveform is incorporated within each period.
It can be seen that the dispersion is further improved compared to cases a) and (b).

Based on these research results, in the present invention, one circumference of the trend surface is made up of multiple pitches with different lengths, and when the pitch length of the shortest pinch is Psin and the pitch length of the longest pitch is P, □ , P, t, l starts at the beginning of the period and ends with the pitch of P*i, l in the next period, including at least one pinch of P, , 8, and P a
The following requirements (11 to (6)) are defined in the case where the basic period starts from the pitch ha and ends at the pitch one pitch before the pitch P at the beginning of the next period.

Here, one period includes at least one pitch of Pl, 8, does not include the pitch of p, □, and the next P a
If the pitch is i+s, the period is further extended to the next period.

+1) When the pitch arrangement within the fundamental period is a Fourier series expansion of a step-like waveform formed by the reciprocal of the pitch length and the pitch length, the second-order or higher-order components are 80% or more of the first-order components. 200% (ratio of 0.8 to 2.0), preferably 100% to 120% (1
, 0-1°2).

Fig. 7 shows the pitch sequence order analysis method within one period.
In the figure, the horizontal axis represents the circumferential length of the tread surface for one cycle, and the vertical axis represents the reciprocal of each of the pitch lengths PC, Pb, P-, and Pa. An array diagram is constructed as shown in FIG. 7 according to the array within one period, and the Fourier series is expanded using the usual method.

In the case of Fourier series expansion in this way, if the second-order or higher-order components are less than 80% of the first-order components, the low-order dispersion effect is small; on the other hand, if it exceeds 200%,
Since the fundamental period is substantially equivalent to having a plurality of periods, pitch noise dispersion deteriorates.

(2) The number of types of pitches within the basic period is 3 to 8, preferably 4 to 6.

This is because if it is less than 2, it is not possible to create a high-order waveform array within the basic period, and if it is more than 9, the mold production cost becomes too high.

(3) The ratio of lengths of adjacent pitches of different pitch lengths within the fundamental period is 1.02 to 1.45. 1°04~
Preferably it is 1.30.

In order to create a high-order waveform array within one fundamental period, the difference in length between adjacent pitches tends to become large, but if the ratio is less than 1.02, an effective modulation effect cannot be achieved; , over 1.45, the difference is too large and causes abnormal wear.

(4) The number of fundamental periods is 1 to 4, preferably 1
~3.

If it is 5 or more, the dispersion of pitch noise becomes poor and it becomes impossible to capture a sufficiently high-order waveform array within the fundamental period. On the other hand, even if the number of fundamental periods is 1, low-order dispersion will be good if a higher-order waveform array is included in the fundamental period.

(5) The pitch arrangement of (1) above, which incorporates 80% to 200% of the 2nd order or higher order components of the 1st order component, occupies 60% or more of the total circumference, preferably 80% or more. thing.

This is because if it is less than 60%, the low-order dispersion effect is small.

(6) The shortest fundamental period is 1/7 of the total circumference
or more. Preferably it should occupy 1/6 or more.

This is because if the length is less than 177, the length is too short and high-order components cannot be sufficiently incorporated.

Furthermore, in the present invention, within one fundamental period, quadratic to primary
At least one component of 0th order, preferably 2nd to 5th order
Preferably, at least one of the following ingredients is present: Components higher than 10th order have little contribution to lower order variance;
This is also because the dispersion of pinch noise may deteriorate.

Examples are shown below.

Exception diameter: 667 IIIm, tire size: 195/80 R
Fourteen steel radial tires (tires of the present invention and conventional tires) were evaluated for noise pulsation width (dB) and quiet feeling. The results are shown in Table 1.
Inside, () means (period length/total length dichotomous representation), (
The numbers in parentheses mean (orders included at a ratio of 0.8 or more to the first order).

Tateno no Koshiki: A method similar to JASOC606-73 tire noise test method, that is, tires were transferred at a speed of 50 km/h on a steel drum with a diameter of 3000 mm (air pressure, rim size, and load were based on JATM 8 standards). The performance was evaluated based on the variation range of the OA value (overall value of noise passed through a band-pass filter of 100 to 2000 Hz) within one rotation of the tire.

FIG. 8 shows the relationship between the order of the periodic array type and the ratio of the order to the first order for a conventional tire. In FIG. 8, Pi, R2, R3°R4 each represent the period, and P
In any period from 1 to P4, first-order components are mainly arranged, and there are extremely few second-order or higher components.

The pitch types are A, B, C, D, and E.

The number of types of pinches is A40. R36, C33, D29
°R26.

PI: EEDDCCBBAAABBCCDD.

R2: EEEDDDCCCBBBBAAABBBCC
CDDDD.

R3: EEDCBBAAABCCDD.

R4: EDCCBABCD.

Full circumference of conventional tire 1: PI +P1 +PL +P1
.

Full circumference of conventional tire 2: R2+P1 +P3 +P4
.

FIG. 9 shows the relationship between the order of the periodic array type and the ratio of the order to one fire component for the tire of the present invention. B3, B4. B5. B6 each represents a period. In any period from Bl to B6, the components of second order or higher are 80% or more of the first order component, and compared to the period of Pi-P4, the components of second order or higher are extremely large. The number of cases has increased. Pitch types are A, B, C, D, and E.
It is. The number of pitch types is A40. B36. C3
3, D29°B26.

Bl　jEEcAABcDcBBcDDBD.

B2 :EEECAAABBCCDDDCCBBBCC
DDDDBBDD.

B3 :EEECAAAABCDCCBBCDDDBBD
YuB4: EECAABBCDCBBCDDD.

B5 :EEECAAAAAABBBCCCDCCCBB
BCCDDDDBBBBDD.

B6 :EEEEECAAAABCCDDDCCCCBB
BBCCDDDBBDDDD.

Entire circumference of the tire l of the present invention: Bl +B1 +B1 +B
1.

The entire circumference of the tire 2 of the present invention: B2 + B3 + B4.

The entire circumference of the tire 3 of the present invention: B5+B6° (margins below this page) The following can be seen from FIGS. 8 and 9 and Table 1. The conventional tire l has one cycle P1 made up of first-order components repeated four times, and there is no modulation in the cycle length, and since Pl is a first-order arrangement, the pulsation width of the noise can be reduced. Since it is large and the pitch noise is not dispersed, it is not practical in terms of feel.

The conventional tire 2 is a combination of linear arrangements in which the periodic length is changed to about 172, about 174, about 175, and about 1/7 over the entire circumference.

Although each periodic length was modulated, since the periodic arrangement was only one-order, the effect of improving pulsation was small, and pulsation was still clearly sensed, making it unsuitable for practical use.

In contrast, the tire 1 of the present invention has an 80
% or more of components also in the second and third order is repeated four times at equal intervals. Because the higher-order components are incorporated into the fundamental period, the number of periods is relatively large, and even though the periods are equal, the pulsation improvement effect is large (and the overall feeling is at a practical level). In the tire 2 of the present invention, the number of cycles is reduced and the cycle length is modulated, and higher-order components are included within the basic cycle.

Therefore, the tire 3 of the present invention, in which pitch noise dispersion was remarkable and both pinch noise and pulsation properties were good, had the pitch noise dispersion improved by further reducing the number of cycles. Since at least higher-order components are included within the fundamental period, there is no problem with pulsation.

〔Effect of the invention〕

As explained above, according to the present invention, since high-order components are incorporated into one basic cycle, the pulsation of low-order noise is improved, and the number of cycles of the entire tire can be reduced. This makes it possible to exhibit a pitch noise dispersion effect and reduce pitch noise.

[Brief explanation of the drawing]

Figure 1 (a), (b), Figure 2 (a), (b), Figure 3 (a), (b), Figure 4 (a). (b), FIG. 5(a), (b), and FIG. 6(a),
(b) is a diagram of the relationship between the pitch array, the order when Fourier analysis is performed, and the amplitude corresponding to that order, Figure 7 is an explanatory diagram showing the pitch array order analysis method within one period, and Figure 8 The figure is a relationship diagram between the order of the periodic array type and the ratio of the order to the first order for a conventional tire, and Figure 9 is the relationship between the order of the periodic array type and the ratio of the order to the first order for the tire of the present invention. Figures 10(a) and 11(a) are explanatory diagrams showing the pitch arrangement, and Figures 10(b) and 11(b) are the orders when performing Fourier analysis, respectively. FIG. 3 is a relationship diagram between the amplitude and the amplitude corresponding to its order. 1... Vibration waveform. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] When one circumference of the tread surface is made up of multiple pitches with different lengths, and the pitch length of the shortest pitch is P_m_i_n and the pitch length of the longest pitch is P_m_a_x,
At least one P between the pitch of P_m_i_n as the beginning of the period and the pitch of P_m_i_n of the next period.
It includes a pitch of __m_a_x, and when the fundamental period starts from the pitch of P_m_i_n and ends at the pitch one pitch before the pitch of P_m_i_n at the beginning of the next cycle,
(1) When the pitch array within the fundamental period is a Fourier series expansion of a step-like waveform formed by the reciprocal of the pitch length and the pitch length, the second-order or higher-order components are 80% of the first-order components. % to 200%, (2) the number of types of pitches in the basic period is 3 to 8, and (3) the ratio of the lengths of adjacent pitches of different pitch lengths in the basic period is 1. 02 to 1.45, (4) the number of the basic periods is 1 to 4, (5) the pitch arrangement occupies 60% or more of the total circumference, (6) the basic period is A pneumatic tire is characterized in that even the shortest tire occupies more than 1/7 of the total circumference.